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As far as this ticket indicates, CouchDB is neither losing precision nor altering the numeric value. It is changing the representation. Thus this is not a bug in CouchDB.

This ticket's opening sentence makes an inaccurate assumption. JSON does not encode "Numbers" (upper-case), like the data type in Javascript. JSON encodes "numbers" (lower-case), what sensible people call real numbers. AFAIK the spec makes no assumptions about how you deserialize and represent that value in your hardware and language.

In other words, just as 1.0 = 1 in arithmetic,

{"a":1}

and

{"a":1.0}

encode the same thing in JSON. If the numeric type is important to you, then store that in the doc. (More often, you'll just type cast.) Or maybe your JSON decoder has an option to disable DWIMming the type.

Consider:

1. What if Couch had returned

{"a":"1.00}

? Would that be a bug? Why not? No fair saying 1.00 is the same type as 1.0 because JSON has no types, only a syntax.

2. Is it a bug if Couch encodes strings greater than 32,767 characters long, the maximum string length in QuickBasic, beyond which there is a runtime error?

Jason Smith
added a comment - 11/Feb/12 15:18 As far as this ticket indicates, CouchDB is neither losing precision nor altering the numeric value. It is changing the representation. Thus this is not a bug in CouchDB.
This ticket's opening sentence makes an inaccurate assumption. JSON does not encode "Numbers" (upper-case), like the data type in Javascript. JSON encodes "numbers" (lower-case), what sensible people call real numbers. AFAIK the spec makes no assumptions about how you deserialize and represent that value in your hardware and language.
In other words, just as 1.0 = 1 in arithmetic,
{"a":1}
and
{"a":1.0}
encode the same thing in JSON. If the numeric type is important to you, then store that in the doc. (More often, you'll just type cast.) Or maybe your JSON decoder has an option to disable DWIMming the type.
Consider:
1. What if Couch had returned
{"a":"1.00}
? Would that be a bug? Why not? No fair saying 1.00 is the same type as 1.0 because JSON has no types, only a syntax.
2. Is it a bug if Couch encodes strings greater than 32,767 characters long, the maximum string length in QuickBasic, beyond which there is a runtime error?

Robert Newson
added a comment - 11/Feb/12 17:22 For my part, I fully accept the notion that we've adhered to the JSON semantics for numbers. However, I think we all recognize that the JSON semantics for numbers are rubbish.
At the very least, as I noted on the 1.2.0 voting thread, this should be recorded in 'BREAKING CHANGES' but I think we ought to fix it. I will devote some cycles to that end.

Filipe Manana
added a comment - 13/Feb/12 15:48 This is the patch I just mentioned in the development mailing list regarding this issue.
It was only barely tested with a few cases, but the full test suite (etap and JavaScript) passes with it.

As mentioned on the dev@ thread, I'm pretty dead set against this approach. While there seems to be some sort of general consensus that storing numbers as uninterpreted bytes and repeating them back is the way to go it really misses the entirety of the issue.

First, CouchDB has never claimed to pass numbers around while keeping byte identical representations. This patch attempts to change that drastically with a very large number of consequences that we haven't begun to investigate.

Secondly, if we were to actually consider going this route then we'd also be obliged to start looking at every other place where we change representations internally as well.

Thirdly, if we were to do that then we'd also have to get into all of the cases where we're stricter than JSON specifically allows and then try and address all of those issues as well.

Basically, how about we just fix the encoder to spit out a decimal point and an appropriate amount of precision and then start documenting our round tripping limitations.

Paul Joseph Davis
added a comment - 13/Feb/12 18:06 As mentioned on the dev@ thread, I'm pretty dead set against this approach. While there seems to be some sort of general consensus that storing numbers as uninterpreted bytes and repeating them back is the way to go it really misses the entirety of the issue.
First, CouchDB has never claimed to pass numbers around while keeping byte identical representations. This patch attempts to change that drastically with a very large number of consequences that we haven't begun to investigate.
Secondly, if we were to actually consider going this route then we'd also be obliged to start looking at every other place where we change representations internally as well.
Thirdly, if we were to do that then we'd also have to get into all of the cases where we're stricter than JSON specifically allows and then try and address all of those issues as well.
Basically, how about we just fix the encoder to spit out a decimal point and an appropriate amount of precision and then start documenting our round tripping limitations.

I've been staying out of the fray so far, but I want to (mostly) endorse
Paul's summary and suggestion. The hear tof my arguemnt is two simple
points:[1] JSON only defines Number. It does not define separate integer and
floating point numbers.[2] CouchDB promises to respond to HTTP requests to PUT and GET data,
and the return value is documented to be JSON.

These two points imply that CouchDB only knows about the kinds of data
structures that JSON defines and supports, and thus can/should make no
promises about the representation of numbers beyond what you can get
from JSON..

If an application depends on the distinction between integers and
floating point values, then it is up to the person writing the
application to make sure this distinction survives. As has already been
pointed out, they can accomplish that goal by storing all numbers as
(JSON) strings and using their application to decode/eval them. This
fix requires no changes to the CouchDB code.

I would not even change the encoder to deal with decimal points and
precision. I would advocate just making sure that the documentation is
clear on this point. In particular, it is probably necessary to
document (as a breaking change that may require people to rewrite some
of their applications) the fact that 1.2 may drop trailing zeros after
the decimal point.

You cannot really promise to support different types of numbers without
radically changing the CouchDB code. You would then have to continually
fight with JSON to get it to support something that is beyond its
capabilities. Maintenance would become a nightmare. Let's try to avoid
that road....

Kevin R. Coombes
added a comment - 13/Feb/12 18:52 I've been staying out of the fray so far, but I want to (mostly) endorse
Paul's summary and suggestion. The hear tof my arguemnt is two simple
points:
[1] JSON only defines Number. It does not define separate integer and
floating point numbers.
[2] CouchDB promises to respond to HTTP requests to PUT and GET data,
and the return value is documented to be JSON.
These two points imply that CouchDB only knows about the kinds of data
structures that JSON defines and supports, and thus can/should make no
promises about the representation of numbers beyond what you can get
from JSON..
If an application depends on the distinction between integers and
floating point values, then it is up to the person writing the
application to make sure this distinction survives. As has already been
pointed out, they can accomplish that goal by storing all numbers as
(JSON) strings and using their application to decode/eval them. This
fix requires no changes to the CouchDB code.
I would not even change the encoder to deal with decimal points and
precision. I would advocate just making sure that the documentation is
clear on this point. In particular, it is probably necessary to
document (as a breaking change that may require people to rewrite some
of their applications) the fact that 1.2 may drop trailing zeros after
the decimal point.
You cannot really promise to support different types of numbers without
radically changing the CouchDB code. You would then have to continually
fight with JSON to get it to support something that is beyond its
capabilities. Maintenance would become a nightmare. Let's try to avoid
that road....
Kevin

Robert Newson
added a comment - 22/Feb/12 16:10 Inclined to agree with the general trend that we don't "fix" this. 1.0 and 1 are the same value, libraries that ignore the consequences of JSON's definition of number are broken and should be fixed.
I'd like to resolve as "Won't Fix" and updated BREAKING CHANGES for 1.2.0 to reflect this decision.

Paul Joseph Davis
added a comment - 22/Feb/12 19:45 Sorry it took so long for me to get to this.
Patch is on 1.2.x and master:
http://git-wip-us.apache.org/repos/asf?p=couchdb.git;a=commitdiff;h=ba271a70b83c6df16af43204c2ba9f4d5ca89711
make check passes locally and a shell session shows it to be correct.